Basic principle of UAV express delivery

There are many kinds of UAV express delivery systems. Now, we will introduce a common system as shown in the figure. The main functions of the core module are as follows:

First, express drones. Unmanned aerial vehicle (UAV) is an eight-rotor aircraft, which is equipped with GPS automatic navigation system, iGPS receiver, various sensors and wireless signal transceiver. UAV has many flight modes, such as GPS automatic navigation, fixed-point suspension and manual control. , and integrated a variety of high-precision sensors and advanced control algorithms such as triaxial accelerometer, triaxial gyroscope, magnetometer and barometric altimeter. The drone is equipped with a black box to record status information. At the same time, the drone also has the function of out-of-control protection. When the UAV is out of control, it will automatically hover accurately, and when it is out of control, it will fly to the nearest express delivery point. UAV transmits data with dispatch center and self-service express cabinet through 4G network and wireless communication remote sensing technology, sends its own geographic coordinates and status information to dispatch center in real time, receives instructions from dispatch center, flies in GPS automatic navigation mode after receiving destination coordinates, and sends landing request, local task report and local operation status report to destination express cabinet after entering the target area. After receiving the response of landing request, express cabinet guides UAV to land on the platform at the top of express cabinet, loading and unloading express delivery, and charging quickly. After no response, the UAV sends a request to the destination transceiver cabinet again, and sends an abnormal landing request report, a local task status report and a local operation status report to the dispatch center after three times of overtime, requesting instructions. After losing contact with the dispatching center or having an abnormal fault, no one will fly to the express delivery point by himself.

Second, the self-service express cabinet. The express cabinet is equipped with computer, UAV queuing decision system, express management system, iGPS positioning system [5], UAV landing guidance system, a loading and unloading express docking platform, eight temporary docking platforms, a mechanical transmission system, four self-service express terminals and multiple express boxes. All the stops at the top of the express cabinet have fast charging function. After the UAV sends landing request, local task report and local operation status report to the express cabinet, the express cabinet inputs the UAV number, UAV task and task priority into the system, and the queuing decision-making system allocates parking platforms, and then the UAV landing guidance system guides the UAV to land, or sends hovering waiting instructions to the UAV. After receiving the landing instruction of the express cabinet, the UAV will continuously transmit the infrared laser positioning signal and the local number received by the iGPS receiver back to the express cabinet, and the express cabinet will accurately grasp the coordinate information of the UAV and guide the UAV to land accurately. When the express cabinet is crowded with drones, it will send a queue congestion report to the dispatch center, and the dispatch center will stop sending loading and unloading instructions to drones. The express cabinet will send the express bill information of the cabinet to the dispatching center in real time, including basic express information, express priority, express receiving time and express congestion status report of the cabinet. According to the degree of business development and cost, express cabinets can be set up in residential quarters, or the express cabinets set up on the roofs of some buildings are also equipped with cameras to monitor and record the environmental conditions around the express cabinets in real time to ensure the safety of users' express delivery and system facilities. The user delivers the courier through the courier cabinet: when the user presses the delivery button, if the courier cabinet is not full, an empty delivery box door will pop up. The user takes out a courier box from the courier box rack, puts the courier box into the courier box, then puts the courier box into the courier box and closes the door. The courier box will detect whether the courier is up to standard, including the detection of weight and danger. If it meets the standard, the user will be prompted to enter the delivery information and delivery grade. After confirming that the destination can be reached, the price is given according to the express weight, delivery distance and delivery priority. Users can pay on the spot, or couriers can pay online or cash on delivery according to their needs. After the courier cabinet completely accepts the courier, it will send the courier information to the courier box via Bluetooth, and the courier box will record the courier information for the identification of the courier. After the drone is docked with the express box, the express box is unloaded, and the express box is brought into the express box by the mechanical transmission device. The courier cabinet will verify the courier according to the UAV mission report and the information in the courier box memory module, and send a short message to remind the user that the courier has arrived, and give a pick-up password and a warm reminder. If the user exceeds the time limit for receiving express delivery, the express box occupancy fee shall be paid according to the overtime time. If the time limit is exceeded, the courier will be returned or transferred to the courier distribution point.

Third, the express box. The express box has built-in Bluetooth and memory module, which is mainly used for parcel express, which is convenient for drones to carry and identify express mail. When the express box is free, put it on the express box rack of the express cabinet, and users can take it by themselves.

Fourth, express delivery points. The distribution point is responsible for the distribution function of express delivery between different regions. The drone receives the instruction from the dispatching center and transports the express delivery from different places to the distribution point. According to the demand, unloading channels can be set up according to the region, and instructions can be issued at different points to guide the drone to land and unload. The unloaded courier will be transported, gathered, packaged and then transported to the airport. At the same time, the dispatch center sends the express information to the dispatch center in each destination area. In addition, the power distribution is also responsible for the security inspection and maintenance of drones, and also has functions such as temporary parking of drones, fast charging, and abnormal express delivery warehouses.

5. Express delivery base. After arriving in this area, the off-site express will be transported to the distribution base. The base will classify the courier according to the courier information in the courier box memory module and transport it to the distribution points in this area. At the same time, the base will put all the arrived express information into storage and send the information to the dispatching center.

Sixth, the regional dispatching center. The dispatching center uniformly manages the receipt and delivery of all couriers in this area and dispatches drones at the same time. At the same time, the dispatching center monitors the running status of the UAV and the self-service express cabinet, and issues corresponding instructions in time according to the strategy in view of its abnormality or congestion. According to the comprehensive consideration of UAV endurance, geographical distribution of express service, real-time reliability of communication, volume and capacity of the system, construction cost and many other factors, the whole system is divided into several areas, which operate independently and cooperate with each other.

One: Express delivery in the area. After receiving the express delivered by the user, the self-service express cabinet sends the receiving information to the dispatching center. The dispatching system selects the appropriate UAV through decision-making, and sends the task instructions and destination coordinates to the UAV. After receiving the instruction, the drone flies to the target, and the courier cabinet will guide the drone to land and automatically load and unload the courier. After the courier is delivered to the destination courier cabinet, the courier cabinet will send the pickup information to the user.

The process is shown in the figure.

Second, cross-regional express delivery. After receiving the express delivery information sent to other regions, the dispatch center will guide the drone to the nearest express delivery point in this region, and will automatically classify the express delivery according to the region, box it and send it to the airport, and the large plane will send it to the express delivery base in the destination region. After receiving the express box, the base will divide it, send the express in the same area to the express delivery point in this area, and then the dispatch center will dispatch the drone to the destination self-service express cabinet.

The core of the deployment strategy shown in the flow chart is to establish the UAV status list, including UAV number, current coordinates, current task status, operation status, endurance and so on. Establish self-service express cabinet status list, including express cabinet number, geographical coordinates, operation status, congestion degree, etc.

The specific method is to generate the arrival schedule of UAVs within a preset radius for each express cabinet by associating the UAV status list with the express cabinet status list, including: the number of UAVs, the estimated arrival time (obtained by counting the loading and unloading time, average flight speed, the current coordinates of UAVs, the current tasks and the coordinates of express cabinets), the estimated endurance time of UAVs, the status of parking spaces, etc. Parking position includes three states: parking on loading and unloading platform, parking on temporary platform and floating state. The table is sorted by arrival time, endurance time and parking space. The setting of radius depends on the statistical optimization of UAV group size, aiming at optimizing the system and shortening the response time. When the UAV group is small, it can be set to the whole area. Establish a list of express delivery teams, including courier code, express cabinet number, destination express cabinet number, required endurance, express priority, etc. , sorted by priority, the priority is determined by the courier level and delivery time.

The process is shown in the figure.

The steps of the scheduling process are as follows:

(1) The UAV sends status information to the dispatching center in real time, and the dispatching center updates the UAV status list in real time;

(2) The courier cabinet sends the receiving information to the dispatching center after receiving the courier, and the dispatching center updates the courier delivery table;

(3) Take out the highest priority express code, express cabinet number and destination express cabinet number from the delivery table;

(4) Take out the endurance and the fastest drone number from the drone arrival schedule of the express cabinet;

(5) The unmanned aerial vehicle in the dispatching center sends an instruction to give the received coordinate position and the released coordinate position;

(6) After the drone reaches the target position, it sends a landing request to the express cabinet;

(7) Using the iGPS positioning system, the express cabinet accurately guides the UAV to dock, land and load and unload express mail;

(8) After the unmanned aerial vehicle (UAV) loads and unloads the goods, it sends a courier report to the dispatching center (or the UAV receives the goods successfully, or the courier is delivered to the destination);

(9) If the task of the UAV is not completed, or there are other tasks to continue, such as: flying to the destination express cabinet to deliver the express, receiving the goods at this express cabinet, or flying away from this express cabinet;

(10) If the UAV has no other tasks, it will receive instructions from the express cabinet to guide and dock on the temporary parking platform, and the express cabinet will issue instructions when receiving landing requests from other UAVs;

(1 1) The courier cabinet will send a courier arrival confirmation report to the dispatch center after the courier enters the cabinet, and at the same time send a mobile phone message to the user to remind the user to collect it in time. The contents include password extraction, overtime charging prompt and returning to the original place.

(12) The courier that has not been taken away beyond the time limit set by the system will be returned to its original place without being checked, and the user will be notified by SMS. The analysis shows that, in order to avoid system congestion and system collapse, the express limit rate of an area is directly proportional to the total number of drones and self-service express cabinets in the area.

As shown in the formula (1), v1= k1× n+k2× m;

(1), where: V 1 is the limit rate of throughput express delivery; K 1 and k2 are coefficients; N is the total number of drones; M is the total number of express cabinets. Further analysis shows that the maximum number of UAVs can be determined by the total number of express cabinets, the maximum number of UAVs handled by express cabinets, and the ultimate flight speed and area of UAVs.

As shown in formula (2): nmax = k× m+k3× (s/v2);

(2) where: Nmax is the maximum number of UAVs; K is the maximum number of drones in the express cabinet; M is the total number of express cabinets; K3 is a coefficient; V2 is the limit flight speed of UAV; S is the area of the area. Therefore, it can be concluded that the focus of the automated UAV express delivery system lies in the layout and construction of self-service express cabinets, and the throughput of the system is ultimately determined by the number of express delivery. Reasonable planning of express cabinets, improving the ability of express cabinets to deal with drones and improving the flight speed of drones can effectively cope with the growth rate of express delivery and optimize various cost resources.